The present invention relates to a human-body-contact, cushioning interface structure. More particularly, it relates to such a structure is designed to be interposed the body and some external structure worn on the body, and through which various kinds of loads (such as shock, general wearing-pressure related, and gravitational) may be applied to the body. While there are many applications wherein the structure of the present invention can offer distinct advantages, a preferred embodiment of the invention is described herein specifically (for illustration purposes) in the setting of a helmet, such as a military helmet, with respect to which the invention has been found to furnish particular utility. For the sake of convenience and simplicity, the description of the invention herein proceeds primarily in the setting of a structural description. That description is effective, in a natural way, to convey an understanding of the associated methodology.
The conventional xe2x80x9cmilitary helmetxe2x80x9d environment is very demonstrative of the issues that are successfully addressed by the present invention. For example, the current U.S.-issue infantry helmet utilizes an internal webbing system combined with a removable leather liner to suspend the helmet on the wearer""s head. Airspace between the webbing and the shell of the helmet greatly contributes to the ballistic, and cooling capabilities of the helmet, but the webbing system has proven consistently to be quite uncomfortable, and thus to be the source of many complaints from users.
Generally speaking, such discomfort comes about principally because of localized capillary circulation loss caused by localized high-pressure points that exist in the contact interface between the helmet and the head. These pressure points come about typically because of poor conformation (uneven pressure distribution) of the usual web-borne head-contacting structure and the shape of the head. Such pressure points generate the complained-of discomfort and pain by creating localized low-blood-concentration ischemia regions in the head.
And so, despite the recognized generally good ballistic and cooling performances of such conventional helmets, their structures, especially in relation to the comfort (or lack thereof) associated with the way in which they are supported on the head, invite significant improvement. Additionally, improvements in ballistic response and/or in cooling, are always welcomed as important advances and contributions.
The structure of the present invention offers improvements in all of these areas of interest. This structure, in one preferred form of the invention, features a novel, multi-layered, web-like cushioning structure which includes different xe2x80x9cfocusedxe2x80x9d layer components that individually address (1) conformance-comfort and ballistic behaviors, (2) moisture-wicking and cooling behaviors, and (3) full moisture-barriering, nonetheless coupled with substantially full gas-flow-enabling, behavior that both guard and enhance the performances associated with matters (1) and (2). The structure of the invention, in relation to the matters of ballistic behavior and comfort, effectively minimizes, substantially to beyond notice, localized high-pressure contact conditions which are the principal creators of discomfort. In the bargain, so-to-speak, of dealing with this issue, the same structural features which vanquish discomfort promote significantly improved ballistic response. Notably, the structure""s improved ballistic behavior remains uncompromised even in the very challenging circumstances of water immersion which can, if not carefully prevented from introducing any moisture into the cushioning core material, appreciably disable the shock-handling capabilities of that material.
Other features of the invention successfully improve the state of the art with respect (a) to minimizing the build-up of heat, (b) to maximizing the dispelling of perspiration, and (c) to enhancing the action of evaporative cooling.
According to one very useful embodiment of the invention, our proposed new structure includes (a) an outer body-contacting layer which is formed of a suitable moisture-wicking material, (b) an anatomically conforming, acceleration-rate-sensitive (preferably viscoelastic), cushion-like structure, or layer, which is disposed closely adjacent the moisture-wicking layer, and (c) a continuous-surface, fully moisture-blocking, yet gas-permeable, barrier layer forming a complete jacketing enclosure, or container, around the viscoelastic layer. The cushion-like rate-sensitive core layer structure can be, selectively, either of a single-component or of a plural-component (plural sublayers) nature, and in the setting of a military helmet, preferably takes the form of two, individual, viscoelastic sublayers which have two different durometers. In this helmet setting, and during use by a wearer, the lower-durometer sublayer is employed closer to the head, and the higher-durometer sublayer is on the opposite side of the lower-durometer sublayer relative to the head, and is interposed the lower-durometer sublayer and the outer external structure which is still on the inside of a helmet. Within, and throughout the full, three-dimensional boundaries of each rate-sensitive, viscoelastic layer, the layer material therein is unfettered in its uniform, omnidirectional performance in response to introduced impact/shock loads. No other structure extends as a nonxe2x80x9chomogeneousxe2x80x9d anomaly through and in this region, which other structure would alter such uniform, all-over, load-response behavior.
In this newly proposed layered structure, the body-contacting (head-contacting in the case of a helmet) moisture-wicking layer effectively draws moisture away from the body. It accomplishes this, in the helmet environment, in a way which is experienced as being superior to the related activity of a conventional helmet support system. The barrier layer forms an uninterrupted continuum enclosing the inside rate-sensitive core material, and thus defines an absolute, limiting boundary for the migration of wicked moisture, preventing it from wetting the rate-sensitive material, and encouraging, at its outer surface, rapid evaporation and attendant cooling. In addition, and as will become apparent, the gas-permeable characteristic of this barrier layer accommodates substantially uncompromised cushioning behavior in the adjacent rate-sensitive, viscoelastic structure.
The cushioning, rate-sensitive, viscoelastic layer structure (two sublayers in the preferred helmet embodiment described herein) furnishes a unique and very effective response both to static and to dynamic (shock/impact/ballistic) loads. This material is temperature and pressure sensitive, and tends to creep (flow laterally) away from hot spots and from localized high-pressure spots. It thus tends to evenize the distributed static (wearing) load, and thus to eliminate, substantially, localized capillary circulation loss, and hence, localized ischemia regions.
Additionally, and very significantly with regard to shock protection, the cushioning layer in the structure of this invention responds (rate-resistantly) to shock-produced, rapid acceleration with a resistance to deformation that generally rises in a somewhat direct relationship to the level of acceleration. This kind of acceleration-rate sensitivity is somewhat analogous to the phenomenon known in the world of fluid mechanics as shear-resistant fluid dilatancy. This behavior causes a shock load to be transmitted to and borne by the body over a relatively wide surface area, and thus generally reduces the likelihood of serious injury. The rate-sensitive core material proposed by the structure of this invention also responds to (and following) an impact event by recovering slowly to an undeformed conditionxe2x80x94thus avoiding any dangerous xe2x80x9creboundxe2x80x9d activity. The important and special rate-resistant, and slow xe2x80x9crecoveryxe2x80x9d, response of this material requires the maintenance of adequate gas-breathability (inflow and outflow) during onset and recovery from deformation, in an environment which also simultaneously guards the material against the infusion of water, or other xe2x80x9csolid-likexe2x80x9d moisture. Moisture infusion would dramatically and negatively affect ballistic-response cushioning behavior.
The layer structure of this invention is easily rendered in a variety of specific configurations, and thus is readily usable in a host of different settings. It is relatively easy and inexpensive to manufacture, and it can be introduced very conveniently in a wide range of xe2x80x9cretrofitxe2x80x9d situations. The specific layer organization of the invention which is chosen for different selected applications is itself an accommodating variablexe2x80x94a variable which enhances the invention""s versatility. For example: overall structure thickness can be different for different circumstances. A single, or more than two, rate-sensitive sublayer(s) can be employed. Within a relatively wide range, a different specific durometer value (or values) for the rate-sensitive sublayer(s) can be chosen. The moisture-wicking layer can be distributed in different ways in the structure to suit different use environments. The moisture-blocking gas-permeable barrier layer can have different selected thicknesses to suit different applications. Importantly, this layer is chosen to be such, that in any situation, such as a water-immersion event, which exposes the proposed new layer structure to significant wetting, no water can penetrate the barrier layer to degrade the shock-managing performance of the rate-sensitive layer material encapsulated inside.
Accordingly, variations from, and modifications of, the invention are recognized to be possible. Several of these are mentioned specifically below.
All of the special features and advantages mentioned above that are offered by the present invention will become more fully apparent as the description which now follows is read in conjunction with the accompanying drawings.